A clean-room implementation of zmq_proxy_steerable().

It is contriubted under the MPL-2.0.

I had no knowledge of the previous implementation of zmq_proxy_steerable().

This version was developed based on expectations set in the old man page with one exception.  This version uses a REP/REQ for the proxy control protocol sockets.  The old man page example used PUB/SUB which is nonsensical given the STATISTICS command requires two way communication.

AUTHORS

@@ -27,6 +27,7 @@ Bernd Prager
 Bob Beaty
 Brandon Carpenter
 Brett Cameron
+Brett Viren
 Brian Buchanan
 Burak Arslan
 Carl Clemens

Makefile.am

@@ -483,6 +483,7 @@ test_apps = \
 	tests/test_issue_566 \
 	tests/test_proxy_hwm \
 	tests/test_proxy_single_socket \
+	tests/test_proxy_steerable \
 	tests/test_proxy_terminate \
 	tests/test_getsockopt_memset \
 	tests/test_setsockopt \
@@ -731,6 +732,10 @@ tests_test_proxy_single_socket_SOURCES = tests/test_proxy_single_socket.cpp
 tests_test_proxy_single_socket_LDADD = ${TESTUTIL_LIBS} src/libzmq.la
 tests_test_proxy_single_socket_CPPFLAGS = ${TESTUTIL_CPPFLAGS}
 
+tests_test_proxy_steerable_SOURCES = tests/test_proxy_steerable.cpp
+tests_test_proxy_steerable_LDADD = ${TESTUTIL_LIBS} src/libzmq.la
+tests_test_proxy_steerable_CPPFLAGS = ${TESTUTIL_CPPFLAGS}
+
 tests_test_proxy_terminate_SOURCES = tests/test_proxy_terminate.cpp
 tests_test_proxy_terminate_LDADD = ${TESTUTIL_LIBS} src/libzmq.la
 tests_test_proxy_terminate_CPPFLAGS = ${TESTUTIL_CPPFLAGS}

doc/zmq_proxy_steerable.txt

@@ -3,7 +3,7 @@ zmq_proxy_steerable(3)
 
 NAME
 ----
-zmq_proxy_steerable - DEPRECATED
+zmq_proxy_steerable - built-in 0MQ proxy with control flow
 
 
 SYNOPSIS
@@ -14,9 +14,102 @@ SYNOPSIS
 
 DESCRIPTION
 -----------
-The _zmq_proxy_steerable()_ function is an empty stub that only returns an
-*EOPNOTSUPP* error, as the author did not provide a relicense agreement for
-the Mozilla Public License v2 relicense of libzmq.
+
+The _zmq_proxy_steerable()_ function is a variant of the _zmq_proxy()_ function.
+It accepts a fourth _control_ socket.  When the _control_ socket is _NULL_ the
+two functions operate identically.
+
+When a _control_ socket of type _REP_ is provided to the proxy function the
+application may send commands to the proxy.  The following commands are
+supported.
+
+_PAUSE_::
+    The proxy will cease transferring messages between its endpoints.
+
+_RESUME_::
+    The proxy will resume transferring messages between its endpoints.
+
+_TERMINATE_::
+    The proxy function will exit with a return value of 0.
+
+_STATISTICS_::
+    The proxy behavior will remain unchanged and reply with a set of simple summary values of the messages that have been sent through the proxy as described next.
+
+There are eight statistics values, each of size _uint64_t_ in the multi-part
+message reply to the _STATISTICS_ command.  These are:
+
+- number of messages received by the frontend socket
+
+- number of bytes received by the frontend socket
+
+- number of messages sent by the frontend socket
+
+- number of bytes sent by the frontend socket
+
+- number of messages received by the backend socket
+
+- number of bytes received by the backend socket
+
+- number of messages sent by the backend socket
+
+- number of bytes sent by the backend socket
+
+
+RETURN VALUE
+------------
+The _zmq_proxy_steerable()_ function returns 0 if TERMINATE is received on its
+control socket.  Otherwise, it returns -1 and errno set to ETERM or EINTR (the
+0MQ context associated with either of the specified sockets was terminated) or
+EFAULT (the provided frontend or backend was invalid).
+
+
+EXAMPLE
+-------
+.Create a function to run the proxy
+----
+// Create the frontend and backend sockets to be proxied
+void *frontend = zmq_socket (context, ZMQ_ROUTER);
+void *backend = zmq_socket (context, ZMQ_DEALER);
+
+// Create the proxy control socket
+void *control = zmq_socket (context, ZMQ_REP);
+
+// Bind the sockets.  
+zmq_bind (frontend, "tcp://*:5555");
+zmq_bind (backend, "tcp://*:5556");
+zmq_bind (control, "tcp://*:5557");
+
+zmq_proxy_steerable(frontend, backend, NULL, control);
+----
+.Code in another thread/process to steer the proxy.
+----
+void *control = zmq_socket (context, ZMQ_REQ);
+zmq_connect (control, "tcp://*:5557");
+
+zmq_msg_t msg;
+
+zmq_send (control, "PAUSE", 5, 0);
+zmq_msg_recv (&msg, control, 0));
+
+zmq_send (control, "RESUME", 6, 0);
+zmq_msg_recv (&msg, control, 0));
+
+zmq_send (control, "STATISTICS", 10, 0);
+while (1) {
+    zmq_msg_recv (&msg, control, 0));
+    printf(" %lu", *(uint64_t *)zmq_msg_data (&msg));
+    if (!zmq_msg_get (&msg, ZMQ_MORE))
+        break;
+}
+printf("\n");
+
+zmq_send (control, "TERMINATE", 9, 0);
+zmq_msg_recv (&msg, control, 0));
+
+zmq_close(frontend);
+zmq_close(backend);
+zmq_close(control);
+----
 
 
 SEE ALSO